Semiconductor device resolution enhancement by etching multiple sides of a mask

ABSTRACT

A mask is disclosed which includes a plurality of first phase shift regions disposed on a first side of the mask, and a plurality of second phase shift regions disposed on a second side of the mask. The first phase shift regions and second phase shift regions may be alternating phase shift regions in which phase shift of the first phase shift regions is out of phase, for instance by 180 degrees, from phase shift of the second phase shift regions. A method for forming the mask, and a semiconductor device fabrication method using the mask is also disclosed.

BACKGROUND OF THE INVENTION

In semiconductor device manufacturing, three-dimensional (3D)integration can be achieved, for instance, using through-substrate vias(TSVs) for chip stacking. Connecting vias between the first metal (forinstance copper) layer and the contact layer is one useful method forachieving such integration, especially for 20 nm technology and beyond.There is a desire to achieve minimum pitch and minimum CriticalDimension (CD) for these connecting vias to create as many possibleconnections between the contact and first metal layers. Currentpractices for forming tightly packed connecting vias uses two reticlesin a double pattern process, in order to achieve the desired points ofconnectivity between the metal and TSV layers.

What is needed is a better facility for providing resolution enhancementfor increased via connection coverage in semiconductor devices. Oneparticularly useful application for this is in maximizing via connectioncoverage area on top of through-substrate vias (TSVs) of a semiconductordevice.

BRIEF SUMMARY

The shortcomings of the prior art are overcome and additional advantagesare provided through the provision of a mask including a plurality offirst phase shift regions disposed on a first side of the mask; and aplurality of second phase shift regions disposed on a second side of themask.

Additionally, a method is provided which includes, for instance, forminga plurality of first phase shift regions disposed on a first side of amask; and forming a plurality of second phase shift regions disposed ona second side of the mask.

Further, a semiconductor device fabrication method is provided whichincludes fabricating a plurality of vias in a semiconductor device, thefabricating including obtaining a mask which includes, for instance, aplurality of first phase shift regions disposed on a first side of themask, and a plurality of second phase shift regions disposed on a secondside of the mask; and subjecting the mask to an exposure ofelectromagnetic radiation, said exposure operative for printing saidplurality of vias onto a substrate of said semiconductor device.

Additional features and advantages are realized through the concepts ofthe present invention. Other embodiments and aspects of the inventionare described in detail herein and are considered a part of the claimedinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

One or more aspects of the present invention are particularly pointedout and distinctly claimed as examples in the claims at the conclusionof the specification. The foregoing and other objects, features, andadvantages of the invention are apparent from the following detaileddescription taken in conjunction with the accompanying drawings inwhich:

FIG. 1 is a schematic representation of one example of a lithographicsystem;

FIG. 2A is one example of a mask having arrayed etched regions forproducing an arrayed via layout on a wafer;

FIG. 2B is a cross-sectional side view of the mask of FIG. 2A takenalong line 2A-2A′;

FIG. 2C is a schematic representation of the intensity profile of lightpassing through the mask of FIG. 2A, taken along line 2A-2A′;

FIG. 3A is one example of a mask in accordance with one or more aspectsof the present invention;

FIG. 3B is a cross-sectional side view of the mask of FIG. 3A takenalong line 3A-3A′;

FIG. 3C is a schematic representation of the intensity profile of lightpassing through the mask of FIG. 3A, taken along line 3A-3A′;

FIG. 4 is a cross-sectional side view of a mask having phase shiftregions of differing width, in accordance one or more aspects of thepresent invention;

FIG. 5 depicts a portion of a mask showing etched regions having a widthand pitch thereof;

FIG. 6A depicts an example of improved pitch achieved using a mask inaccordance with one or more aspects of the present invention; and

FIG. 6B depicts an example of increased etch size achieved using a maskin accordance with one or more aspects of the present invention.

DETAILED DESCRIPTION

The semiconductor or integrated circuit (IC) industry aims tomanufacture ICs with higher and higher densities of devices on a smallerchip area to achieve greater functionality and to reduce manufacturingcosts. This desire for large scale integration has led to a continuedshrinking of circuit dimensions and device features. The ability toreduce the size of such features is driven by performance enhancementsin the lithographic process by which integrated circuit (IC) structuresare formed on a wafer. This process is also referred to asphotolithography, or simply lithography. As is well known, lithographicprocesses can be used to transfer a pattern of a photomask (i.e. “mask”,also referred interchangeably herein as a “reticle”) to a wafer.

In one example, patterns are formed from a photoresist layer disposed onthe wafer by passing radiation energy through a mask having anarrangement to image the desired pattern onto the photoresist layer. Asa result, the pattern is transferred to the photoresist layer. In areaswhere the photoresist is sufficiently exposed, and after a developmentcycle, the photoresist material can become soluble such that it can beremoved to selectively expose an underlying layer (e.g., a semiconductorlayer, a metal or metal containing layer, a dielectric layer, a hardmask layer, etc.). Portions of the photoresist layer not exposed to athreshold amount of radiation energy will not be removed, and will serveto protect the underlying layer during further processing of the wafer(e.g., etching exposed portions of the underlying layer, implanting ionsinto the wafer, etc.). Thereafter, the remaining portions of thephotoresist layer can be removed. Although the above refers to apositive resist process, negative resist processes can also be utilizedto pattern a photoresist layer. Further details of a lithographicprocess are described below in connection with the lithographic systemof FIG. 1.

The lithographic system 100 of FIG. 1 is suitable for use in patterninga wafer 102. Lithographic system 100 includes a chamber 104, a radiationsource 106 (typically a light source), a condenser lens assembly 108(labeled “OPTICS” in FIG. 1), a mask or a reticle 110, an objective lensassembly 112 (labeled “OPTICS” in FIG. 1), and a stage 114. Lithographicsystem 100 is configured to transfer a pattern or image provided on mask110 to a target material or surface of wafer 102.

Wafer 102 includes a substrate 116, a layer 118, and a photoresist layer120. Photoresist layer 120 is disposed over layer 118, and layer 118 isdisposed over substrate 116. Wafer 102, as depicted in FIG. 1, can be anentire semiconductor wafer or a portion thereof. Substrate 116 can be asemiconductor substrate, such as silicon, gallium arsenide, germanium,or any suitable substrate material. Substrate 116 can include one ormore layers of material and/or features, such as lines, interconnects,vias, doped regions, or the like, and substrate 116 can further includedevices or portions thereof, such as transistors, microactuators,microsensors, capacitors, resistors, diodes, or the like.

Layer 118 can be an insulative layer, a conductive layer, a barrierlayer, or any target material to be etched, doped, treated, processed,or layered. In certain embodiments, layer 118 is a hard mask layer, suchas a silicon nitride layer or a metal layer. The hard mask layer canserve as a patterned layer for processing substrate 116 or forprocessing a layer upon substrate 116. In yet another embodiment, layer118 is an anti-reflective coating (ARC). Substrate 116 and layer 118 arenot described in a limiting fashion, and can each include a conductive,semiconductive, or insulative material.

Photoresist layer 120 can include a variety of photoresist materials,compositions, or chemicals suitable for lithographic applications.Photoresist layer 120 is selected to have photochemical reactions inresponse to electromagnetic radiation (also referred to herein as‘light’) emitted from radiation source 106 and to have sufficienttransparency to the electromagnetic radiation to allow useful patterningof the photoresist layer. Materials including photoresist layer 120 caninclude, among others, a matrix material or resin, a sensitizer orinhibitor, and a solvent. Photoresist layer 120 may be a chemicallyamplified, positive or negative tone, organic-based photoresist.Photoresist layer 120 may also be a silicon-containing photoresist.Photoresist layer 120 may be, but is not limited to, an acrylate-basedpolymer, an alicyclic-based polymer, or a phenolic-based polymer.

Photoresist layer 120 is formed over the target material or layer ofwafer 102 using any suitable technique, for example, deposition by spincoating over layer 118. The thickness of photoresist layer 120 isselected according to the particular lithographic technology, e.g., foruse in vacuum ultraviolet (VUV) lithography, deep ultraviolet (DUV)lithography, and/or extreme ultraviolet (EUV) lithography (using, forexample, exposing radiation having a wavelength of 193 nm, 157 nm, 126nm, or 13.4 nm). In this regard, photoresist layer 120 may have athickness in the range of 15-1000 nm.

Radiation source 106 provides electromagnetic radiation throughcondenser lens assembly 108, mask 110, and objective lens assembly 112to photoresist layer 120. In one embodiment, radiation source 106 may bean excimer laser that produces radiation having a wavelength of 248 nm,193 nm, 172 nm, 157 nm, or 126 nm, or a soft x-ray source that producesradiation having a wavelength of 13.4 nm. Alternatively, radiationsource 106 may be any suitably configured radiation source capable ofemitting radiation having a wavelength in the ultraviolet (UV), VUV,DUV, EUV, or x-ray range. Alternatively, the system may utilize asuitably configured electron/ion beam source.

Assemblies 108 and 112 include lenses, mirrors, collimators, beamsplitters, and/or other optical components to suitably focus and directa pattern of radiation (i.e., radiation from radiation source 106 asmodified by a pattern or image provided on mask 110) onto photoresistlayer 120. Stage 114 supports wafer 102 and can move wafer 102 relativeto assembly 112.

Mask 110 is a binary mask in one embodiment. Mask 110 includes atransparent or translucent substrate 122 (e.g., glass or quartz) and anopaque or patterned layer 124 (which may be formed from chromium orchromium oxide, as examples) thereon. Opaque layer 124 provides apattern or image associated with a desired circuit pattern, features, ordevices to be projected onto photoresist layer 120. In one embodiment,mask 110 is an alternating phase shift mask, or other type of mask.

As light waves from light source 106 pass to mask 110, light incidentupon the translucent areas of the mask will pass through the mask, whilelight incident on the opaque areas will be blocked. Light passingthrough the mask exposes portions of the photoresist layer 120 of thewafer 121.

There is a pervasive trend in the art of IC fabrication to increase thedensity with which various structures are arranged. For example, featuresize, line width, and the separation between features and lines arebecoming increasingly smaller. Yield is affected by factors such as maskpattern fidelity, optical proximity effects, and photoresist processing.

Resolution enhancement is provided herein in accordance with aspects ofthe present invention. One particularly useful application forresolution enhancement is the via connection area on top ofthrough-substrate vias (TSVs). TSVs are relatively large—typically about6 microns on top, with the dip being a few hundred microns. While asingle solid metal connection on the top of the TSV would provide thebest connectivity, that approach does not work. Instead, atwo-dimensional (2D) array of thinner vias (for instance about 45 nmeach) leading to the TSV is formed for connectivity with the upperlayer(s) of the device. The vias in the 2D array of vias should be ascompact as possible (i.e. have a closest possible pitch) to increase thenumber of vias formed on top of the TSV, thereby increasing the contactarea and lowering resistance while avoiding stress-induced void.

A conventional mask having arrayed etched regions for producing anarrayed via layout on a wafer is depicted and described with referenceto FIGS. 2A and 2B. FIG. 2A depicts a top view of mask 200. Mask 200includes opaque material 202 deposited over a translucent substrate 206(FIG. 2B). Regions 204 are etched into opaque material 202 to create aplurality of etched regions 204 arrayed in two directions (verticallyand horizontally in this example). Mask 200 depicts only nine etchedregions 204, but a typical mask may include many hundreds or thousandsof such etched regions.

The etching of regions 204 typically involves chemically and/ormechanically removing portions of opaque material 202 to expose asurface of the underlying translucent substrate. This is illustrated inFIG. 2B which depicts a cross-sectional side view of mask 200 takenalong line 2A-2A′. The cross-section depicts regions 204 etched throughopaque material 202 to translucent substrate 206. Etched regions 204 areseparated by opaque material 202.

As light is introduced to mask 200 (e.g. vertically from above themask), the light incident on opaque material 202 will be substantiallyblocked from passing through substrate 206 to the photoresist area ofthe wafer, while light passing through etched regions 204 and incidenton the exposed portion of substrate 206 will pass through substrate 206to the photoresist area. The exposure will form a corresponding patternof vias in the photoresist area of the wafer.

Light intensity will vary across portions of the wafer depending onwhether those portions were exposed or not to light passing through thesubstrate. FIG. 2C is a schematic representation of the intensityprofile of light passing through mask 200 of FIG. 2A, taken along line2A-2A′. The intensity profile is shown to vary in a binary fashionbetween 0 and 1 for simplicity, with the 0 indicating areas (such asdirectly beneath the opaque material 202) experiencing no, or relativelylittle, light exposure, and the 1 indicating areas (such as beneath theetched regions 204) experiencing intense, or relatively high, lightexposure. Ignoring the effects of diffraction, an appropriate ‘shadow’corresponding to mask 200 will be projected to the wafer beingpatterned.

In practice, however, light incident upon the various areas of theresist layer of the wafer is impacted by diffracted light from edgesbetween the etched areas and the opaque areas of the mask. By decreasingthe distances between the opaque areas, small apertures are formed whichdiffract the light that passes through the apertures. The diffractedlight results in effects that tend to spread or to bend the light as itpasses through the mask, so that the space between the two opaque areasis not resolved. This makes diffraction a limiting factor for opticalphotolithography since the light/dark contrast of the ‘shadow’ beingprojected is negatively impacted. This becomes more problematic as thepitch (on-center spacing) between etched regions of the mask decreasesto accommodate more tightly-arranged features to be printed on thewafer.

A way of dealing with the effects of diffraction is through lightphase-shifting, as is appreciated by those having ordinary skill in theart. In phase-shifting, the mask is fabricated so as to cause a phaseshift in some of the light passing through the translucent substrate.Interference between light waves is reduced when those waves are out-ofphase. So, when the phase of light exposing one region of the wafer isshifted from the phase of light exposing an adjacent region, theinterference is minimized, contrast is improved, and the resolutioncapability achievable using the mask is increased.

Varying the thickness of the mask substrate in some translucent regionsof the mask is one way of causing such a phase shift. Regions of varyingdepth can be etched onto a frontside of a mask to introduce varyingdegrees of phase shift in the light passing through the substratethereof. With reference again to FIGS. 2A and 2B, some regions 204 mayextend into a portion of the underlying substrate 206, decreasing thethickness of substrate 206 under that etched region 204 and introducinga shift in phase relative to the light passing through other (thicker)areas of the substrate under other etched regions thereof.

In accordance with an aspect of the present invention, a mask isprovided having a plurality of first and second phase shift regions. Inone example, the first phase shift regions are disposed on a first sideof the mask by etching the first side, while the second phase shiftregions are disposed on a second side of the mask by etching the secondside. FIG. 3A depicts one example of a mask in accordance with one ormore aspects of the present invention.

Phase shift mask 300 includes opaque material 302, such as molybdenumsilicon nitride (MoSiN), deposited over translucent substrate 306 (FIG.3B), such as quartz. First phase shift regions 304 are arrayed andaligned in two directions—vertically and horizontally in this diagram—asare second phase shift regions 308. Second phase shift regions are 180degree phase shift regions in this example, however second phase shiftregions 308, like first phase shift regions 304, could have any desiredphase shift.

FIG. 3B shows a cross-sectional side view of mask 300 of FIG. 3A takenalong line 3A-3A′. First phase shift regions 304 are disposed (e.g. byetching) on the side of the mask on which opaque material 302 isdeposited. For convenience, this side of mask 300 is referred to as thefrontside of the mask. The frontside of the mask is additionally etchedbetween first phase shift regions 304, and vertically above second phaseshift regions 308. Etching the frontside of the mask above second phaseshift regions 308 exposes the substrate above second phase shift regions308 in order to enable light to pass through the mask and second phaseshift regions 308. Second phase shift regions 308 are disposed (byetching) on the opposite side (e.g. backside) of the mask, in thisexample. Etching second phase shift regions 308 into the backside of thesubstrate 306 provides a thinner area of translucent substrate at thesecond phase shift regions 308 than at the first phase shift regions304. Consequently, phase shift regions 304 and 308 will have (i.e.produce) different shifts in the phase of light when light passestherethrough; that is, the phase shift produced by second phase shiftregions 308 will differ from phase shift produced by the first phaseshift regions 304.

In one example, it may be desired for the phase shift of first phaseshift regions 304 to be 180 out of phase with the phase shift of secondphase shift regions 308. In particular, first phase shift regions 304may have a 0 degree (or substantially no) phase shift, meaning no shiftin phase is introduced by that regions as light passes through thesubstrate at that region. A phase shift region producing no (orsubstantially no) phase shift may also be referred to as a “non-phaseshift region”. Additionally or alternatively, second phase shift regions308 may have a 180 degrees (or substantially 180 degrees) phase shift.Thus, in one particular example, first phase shift regions 304 may beformed so as to produce no (i.e. 0 degree) phase shift while secondphase shift regions 308 may be formed so as to produce a 180 degreesphase shift. The 180 degrees difference in phase between first andsecond phase shift regions, 304 and 308 respectively, will maximize thecancelling effect and minimize interference between light waves comingfrom first phase shift regions 304 and light waves coming from secondphase shift regions 308.

Though FIG. 3A depicts only nine phase shift regions, it is understood,as noted above, that a typical mask may include many hundreds orthousands of such phase shift regions.

Additionally with respect to FIG. 3A, it is seen that adjacent firstphase shift regions 304 are spaced apart not only by areas of opaquematerial 302 on the frontside of the mask, but also by second phaseshift regions 308 on the backside of the mask. Similarly, adjacentsecond phase shift regions 308 on the backside of the mask are spacedapart by opaque material 302 and first phase shift regions 304, both onthe frontside of mask 300.

FIG. 3C is a schematic representation of the intensity profile of lightpassing through the mask of FIG. 3A, taken along line 3A-3A′. Theintensity profile varies between −1, 0, and 1, accounting not only forthe presence or absence of light, but also for the difference in thephase of light passing through first phase shift regions 304 and thephase of light passing through second phase shift regions 308. Theintensity profile of FIG. 3C is produced when first phase shift regions304 are 180 degrees out of phase of second phase shift regions 308 (i.e.the difference in the phase of light passing through regions 304 and thephase of light passing through regions 308 is 180 degrees). In thatcase, a 1 indicates areas (such as beneath etched regions 304)experiencing intense, or relatively high, light exposure, a 0 indicatesareas (such as directly beneath the opaque material 302) experiencingno, or relatively little, light exposure, and a −1 indicates areas (suchas beneath etched regions 308) experiencing intense, or relatively high,light exposure by light that is 180 degrees out-of-phase from the lightpassing through first phase shift regions 304.

Resolution capability of the mask of FIG. 3A is increased by 2× due tothe higher contrast potential between the first phase shift regions(intensity of 1) and the second phase shift regions (intensity of −1).From a layout perspective, the additional contrast allows spacingbetween phase shift regions (and therefore the spacing between the viasformed on the wafer) to be decreased, thereby increasing the resolutionachieved using the mask. Further detail is provided below with referenceto FIGS. 6A and 6B.

In accordance with aspects of the present invention, and in contrast toconventional techniques of etching only a single side of the mask, asecond side of the mask (for instance, the underside of the substrate)is etched in order to introduce the desired phase shift of the secondphase shift regions. One advantage to etching the backside of the maskis that fewer process steps, as compared to a multiple reticleconfiguration, are needed in the fabrication of the mask and during thelithographic process to expose a wafer. Alternating phase shift regionsare provided using only a single mask, and vias can be formed from asingle exposure using that single mask. This is advantageous over, forinstance, the double reticle processes where two reticles are fabricatedand utilized in a double-patterning process.

Also, greater leeway is afforded for deviation from the criticaldimensions of the second phase shift region etches on the backside. Thisis illustrated in FIG. 4, which depicts a cross-sectional side view of amask having phase shift regions of differing width, in accordance one ormore aspects of the present invention. In this example, first phaseshift regions 404 are disposed as etches of width W₁, while second phaseshift regions 408 are disposed as etches of width W₂. First phase shiftregions 404 and the openings above second phase shift regions 408 areetched with relatively high precision having width W₁, for instance,because the light strikes the mask from above (in this diagram). Sincethe light is incident on the frontside of the mask having opaqueblocking material 402, the second phase shift regions 408 can be etchedwider than these etchings above second phase shift regions 408. There ismore tolerance for error when etching the backside of the mask in thiscase because the opaque material above will serve as a mask for blockinglight outside of that opening. Provided that the etching on the backsideof the mask does not extend to directly beneath any first phase shiftregion 404, the second phase shift regions 408 can be purposelyoversized (i.e. W₂) to hedge against possible failure conditions inmeeting the target W₂; so long as second phase shift region 408 is atleast as wide as W₁ and is narrow enough that it does not extend beneathany first phase shift region 404, this is acceptable. In this regard,there are, in one embodiment, upper and lower bounds on the width W₂ ofa second phase shift region 408 a. The lower bound is the width (W₁ inthe example of FIG. 4) of the frontside opening directly (vertically)above second phase shift region 408 a (i.e. between the right edge ofopaque material 402 a and left edge of opaque material 402 b). The upperbound is the distance between the right edge of first phase shift region404 a and the left edge of first phase shift region 404 b. In thedepiction of FIG. 4, then, second phase shift region 408 a couldextended from below the right edge of first phase shift region 404 a tobelow the left edge of first phase shift region 404 b. In this manner,there is more tolerance in fabrication of the backside etchings (408)than fabrication of the frontside etchings (404). The backside etchingsmight be wider or misaligned (off-center between opaque material 402 aand 402 b), as examples, without affecting the efficacy of the secondphase shift regions.

As noted above, the additional contrast afforded by aspects of thepresent invention advantageously enables the spacing between phase shiftregions to be reduced. To illustrate, and turning to FIG. 5, depicted isa portion of a mask showing etched regions having a width and pitchthereof. Mask 502 includes multiple etched regions 504 having width, W,and being spaced apart by distance, D (D is the “pitch” between etchedregions 504). Aspects of the present invention advantageously provideresolution enhancement that enables, for instance, pitch between phaseshift regions to be reduced and/or phase shift regions size increased,which is directly proportional to an decrease in pitch and increase infeature size of features (e.g. vias) printed on a wafer. Such pitch andsize enhancements thereby increase coverage area of the array of viasproduced using the mask.

The minimum pitch of the vias produced using a mask in accordance withaspects of the present invention can be reduced by as much as 50% insome cases. FIG. 6A depicts an example of improved pitch achieved usinga mask according to one or more aspects of the present invention. By wayof example and not limitation, first phase shift regions 604 a of FIG.6A are 0 degrees phase shift regions of a mask and second phase shiftregions 608 a are 180 degrees phase shift regions of the mask. In thiscase, width W′ of phase shift regions 604 a and 608 a remains the samecompared with FIG. 5, but pitch between adjacent regions (of differingphase shift) is reduced. Pitch D′ of FIG. 6A is smaller than pitch Dfrom FIG. 5, where first and second phase shift regions, 504 a and 508 arespectively, are spaced closer together without adversely affectingcontrast. This is because of the cancellation effects due to thedifferences in phase between light passing through first phase shiftregions 604 a and light passing through second phase shift regions 608a, as explained above.

FIG. 6B illustrates increased etch size for resolution enhancement.Again by way of example and not limitation, first phase shift regions604 b of FIG. 6B are 0 degrees phase shift regions of a mask and secondphase shift regions 608 b are 180 degrees phase shift regions of themask. In this example, pitch remains the same as in FIG. 5 (D″=D). Firstphase shift regions 604 b and second phase shift regions 608 b are madelarger (W″), thus increasing the coverage area of vias produced by thesephase shift regions. In a further embodiment, both pitch and featuresize can be modified (i.e. pitch is decreased, and size of first andsecond phase shift regions is increased) in combination, in order toincrease via coverage area.

In alternative embodiments, the first and second phase shift regions maybe, if desired, etched onto a same side of the mask. In such aconfiguration, the second phase shift regions are disposed between firstphase shift regions on the frontside of the mask by etching the secondphase shift regions into the substrate on the frontside instead ofetching on the backside of the mask. The configuration produced is thecheckerboard pattern as depicted in FIG. 3A, which the difference beingthat second phase shift regions are disposed on the frontside ratherthan the backside, and are disposed as deeper etches (in one example) inthe frontside of the mask than the etches forming the first phase shiftregions in the frontside of the mask.

An increase in the coverage area of vias produced using a single mask,in accordance with aspects of the present invention, is advantageouslyprovided. Whereas conventional approaches use two or more reticles tominimize pitch and/or maximize feature size, aspects of the presentinvention advantageously enable such enhancements using a single mask.

Aspects of the present invention additionally include methods forfabricating a mask having the configuration(s) described above, andmethods for semiconductor device fabrication using such a mask.Accordingly, a mask fabrication method may include forming multiplefirst phase shift regions disposed on a first side of the mask, andforming a plurality of second phase shift regions disposed on a secondside of the mask, as described above. Additionally, a semiconductordevice fabrication may include procuring a mask as described above andsubjecting the mask to an exposure of electromagnetic radiation using,for instance the technique described above with reference to FIG. 1, toprint vias onto a substrate of the semiconductor device.

The terminology used herein is for the purpose of describing particularembodiments only and is not intended to be limiting of the invention. Asused herein, the singular forms “a”, “an” and “the” are intended toinclude the plural forms as well, unless the context clearly indicatesotherwise. It will be further understood that the terms “comprise” (andany form of comprise, such as “comprises” and “comprising”), “have” (andany form of have, such as “has” and “having”), “include” (and any formof include, such as “includes” and “including”), and “contain” (and anyform contain, such as “contains” and “containing”) are open-endedlinking verbs. As a result, a method or device that “comprises”, “has”,“includes” or “contains” one or more steps or elements possesses thoseone or more steps or elements, but is not limited to possessing onlythose one or more steps or elements. Likewise, a step of a method or anelement of a device that “comprises”, “has”, “includes” or “contains”one or more features possesses those one or more features, but is notlimited to possessing only those one or more features. Furthermore, adevice or structure that is configured in a certain way is configured inat least that way, but may also be configured in ways that are notlisted.

The corresponding structures, materials, acts, and equivalents of allmeans or step plus function elements in the claims below, if any, areintended to include any structure, material, or act for performing thefunction in combination with other claimed elements as specificallyclaimed. The description of the present invention has been presented forpurposes of illustration and description, but is not intended to beexhaustive or limited to the invention in the form disclosed. Manymodifications and variations will be apparent to those of ordinary skillin the art without departing from the scope and spirit of the invention.The embodiment was chosen and described in order to best explain theprinciples of one or more aspects of the invention and the practicalapplication, and to enable others of ordinary skill in the art tounderstand one or more aspects of the invention for various embodimentswith various modifications as are suited to the particular usecontemplated.

What is claimed is:
 1. A mask comprising: a plurality of first phaseshift regions disposed on a first side of the mask; and a plurality ofsecond phase shift regions disposed on a second side of the mask,wherein each second phase shift region of the plurality of second phaseshift regions is centered in alignment with a respective gap betweenopaque regions disposed on the first side of the mask, the gap andopaque regions separating adjacent first phase shift regions of theplurality of first phase shift regions.
 2. The mask of claim 1, whereina phase shift of the plurality of first phase shift regions is out ofphase with a phase shift of the plurality of second phase shift regions.3. The mask of claim 2, wherein the phase shift of the plurality offirst phase shift regions is approximately 180 degrees out of phase withthe phase shift of the plurality of second phase shift regions.
 4. Themask of claim 1, wherein a first phase shift region of the plurality offirst phase shift regions has a zero degree phase shift.
 5. The mask ofclaim 1, wherein a second phase shift region of the plurality of secondphase shift regions has a 180 degrees phase shift.
 6. The mask of claim1, wherein the plurality of first phase shift regions and the pluralityof second phase shift regions are aligned in at least one directionacross the mask, and spaced apart in an alternating fashion in the atleast one direction across the mask.
 7. The mask of claim 6, wherein theplurality of first phase shift regions and the plurality of second phaseshift regions are aligned in a first direction and a second directionorthogonal to the first direction.
 8. The mask of claim 1, wherein thefirst side comprises a frontside of the mask and the second sidecomprises a backside of the mask, and wherein the plurality of firstphase shift regions are formed by etching the frontside of the mask andthe plurality of second phase shift regions are formed by etching thebackside of the mask.
 9. The mask of claim 1, wherein a width of theplurality of second phase shift regions is greater than a width of theplurality of first phase shift regions.
 10. The mask of claim 1, whereinfirst phase shift regions of the plurality of first phase shift regionsand second phase shift regions of the plurality of second phase shiftregions are spaced apart by an opaque material deposited on the firstside of the mask.
 11. The mask of claim 10, wherein the opaque materialis disposed over a first side of a translucent substrate, and whereinthe plurality of second phase shift regions are formed by etching asecond side of the translucent substrate.
 12. The mask of claim 1,wherein a pair of opaque regions reside adjacent a gap with which asecond phase shift region of the plurality of second phase shift regionsis in center-alignment, and wherein the second phase shift regionextends in a first direction past a center of one opaque region of thepair of opaque regions.
 13. The mask of claim 12, wherein the secondphase shift region extends in a second direction past a center of theother opaque region of the pair of opaque regions.
 14. A methodcomprising: forming a plurality of first phase shift regions disposed ona first side of a mask; and forming a plurality of second phase shiftregions disposed on a second side of the mask, wherein each second phaseshift region of the plurality of second phase shift regions is centeredin alignment with a respective gap between opaque regions disposed onthe first side of the mask, the gap and opaque regions separatingadjacent first phase shift regions of the plurality of first phase shiftregions.
 15. The method of claim 14, wherein a phase shift of theplurality of first phase shift regions is out of phase with a phaseshift of the plurality of second phase shift regions.
 16. The method ofclaim 14, wherein forming the plurality of first phase shift regions andforming the plurality of second phase shift regions comprises aligningthe plurality of first phase shift regions and the plurality of secondphase shift regions in at least one direction across the mask, andspacing apart the plurality of first phase shift regions and theplurality of second phase shift regions in an alternating fashion in theat least one direction across the mask.
 17. The method of claim 14,wherein the first side comprises a frontside of the mask and the secondside comprises a backside of the mask, and wherein forming the pluralityof first phase shift regions comprises etching the frontside of themask, and forming the plurality of second phase shift regions comprisesetching the backside of the mask.